The ad slogan "Bet you can't eat just one" is pretty accurate — and not because Lay's potato chips are particularly delicious. A new study found that the fats in foods like chips and french fries make the body produce a chemical with qualities similar to marijuana that give people a case of what's technically known as "the munchies."

Recently researchers presented a shocking new finding: Regularly eating an entire bag of potato chips leads to weight gain. A new study by scientists at UC Irvine explains why: The fats in these foods makes the body produce weed-like chemicals called endocannabinoids. From EurekAlert:

In their study, the Piomelli team discovered that when rats tasted something fatty, cells in their upper gut started producing endocannabinoids. Sugars and proteins, the researchers noted, did not have this effect.

The process starts on the tongue, where fats in food generate a signal that travels first to the brain and then through a nerve bundle called the vagus to the intestines. There, the signal stimulates the production of endocannabinoids, which initiates a surge in cell signaling that prompts the wanton intake of fatty foods, Piomelli said, probably by initiating the release of digestive chemicals linked to hunger and satiety that compel us to eat more.

According to lead researcher Daniele Piomelli, this process served an important biological purpose in the days when every cave and hut didn't contain a stockpile of junk food. The body needs fats, which are scarce in nature. The process gave early humans the push they needed to get up and hunt for more fatty foods rather than lounging in front of the fire and stuffing their faces with berries all day. Unfortunately, now that drive just convinces us to walk 10 feet to the pantry and rip open another bag of chips. The researchers hope to develop a drug to block endocannabinoid activity so fatty foods' natural deliciousness and the fact that we just don't give a damn will be the only things pushing us to stuff ourselves.